The invention generally relates to a method of manufacturing hollow, reinforced plastic composite articles, and, more particularly, to a method of cooling a core inserted into a preform for the purpose of manufacturing fiber reinforced pressure vessels for the storage, treatment, and transportation of liquids. According to this invention, the term xe2x80x9ccorexe2x80x9d is meant to include an inflatable rubberized core such as a flexible bag or a plastic liner. This cooling method prevents the deterioration of the inflatable core or the deformation and deterioration of the plastic liner used during the manufacture of the pressure vessel.
Plastic composite articles are becoming increasingly important in a variety of industries, showing many advantages over other materials such as metals and ceramics. Fiber-reinforced plastic composite articles can utilize a number of materials in their composition, including glass, carbon, metal, ceramics, and plastics for reinforcing materials with thermosetting or thermoplastic materials used as binding materials.
Various methods exist for manufacturing reinforced plastic composite articles. The prior art discloses a variety of methods for manufacturing hollow, cylindrical, fiber-reinforced composite articles utilizing both thermosetting resins and thermoplastics for binding reinforcing materials. Many of these manufacturing methods require the heating of a preform of thermoplastic molding fibers and reinforcing fibers, such as glass, while in a rigid mold, to create the finished article. Typically, a plastic liner or rubberized core is installed within the preform, and inflated with a gas while the preform is being heated in the mold to fuse the thermoplastic. As the preform is heated, the core or liner is used to maintain the shape of the preform, and urge the preform against the mold wall. The liner or core then defines the interior shape of the preform.
In some cases, it is desirable that the core be partially or completely bonded to the interior of the preform and thus become part of the finished article, providing a special interior surface. In other cases, the core is removed from the article after the article is cooled, whereby the core may preferably be reused.
However, since the preform within the mold may need to be heated to relatively high temperatures, such as 300 or more degrees F., sometimes for 30 or more minutes when the binding material is a thermoplastic resin, the core may undergo undesirable transformations due to the heating process.
For example, if an inflatable rubberized core is used, such as a neoprene or silicone rubber bladder, the heating process within the mold may lead to a deterioration of the core. The core may become brittle, less-resilient, and deformed. If the core is to be removed from the finished article and reused, it will show a reduced life cycle and is more prone to failure during use, thus increasing the risk of a faulty finished article. If the core is to become a part of the finished article, it may gain undesirable properties (such as deformation, brittlization, material transformation, etc.) due to the effects of heating the core.
A similar situation occurs when a plastic liner is used in the interior of the article. Since it is often desirable that the plastic liner be of a similar thermoplastic resin material as the finished article, the liner will soften and lose its shape as the preform is heated. The heat will tend to soften and melt the liner, even if the liner is pressurized to maintain its shape. However, that softening and melting may lead the liner resins to intermix with the preform and be absorbed, so that the properties of the special lining are lost.
It would be desirable to provide a method to prevent these deleterious effects on the inflatable rubberized cores and plastic liners in the manufacture of plastic composite pressure vessels.
This method and device provides a cooling means for the interior of a hollow, reinforced plastic composite article while simultaneously pressurizing the interior of the article during a heating process. This is done by providing a back pressure valve on a pressure outlet line of the core and using a fluid such as water to circulate through the liner to pressurize and cool the core contained in the interior of the article. This helps keep the interior of the article cool and preserves the life and condition of the inflatable core while the article is being heat treated. This method can also be used to pressurize and cool a liner or similar component of article during heat treating, consolidation, or cure of the article.